Publications and other reference materials referred to herein, including reference cited therein, are incorporated herein by reference in their entirety and are numerically referenced in the following text and respectively grouped in the appended Bibliography which immediately precedes the claims.
Phase transitions are important and frequently useful because they bring about sharp changes in material properties. Usually the trigger for a phase transition is a change in the ambient temperature or pressure. A phase transition can also be induced by the action of external fields such as magnetic or electric fields or gravity. The effect of a uniform electric field on the phase diagram of liquid mixtures was considered many years ago by Landau and Lifshitz, who predicted that for mixtures of simple liquids an electric field will raise the critical temperature Tc by a minuscule amount (typically <0.01K), usually resulting in phase separation [1]. In their treatment, the change in Tc resulted from the non-linear dependence of the dielectric constant ∈ on the mixture composition. However, experiments dating back to Debye and Kleboth [2] have shown that, on the contrary, the application of an electric field induces mixing.
The inventor has previously shown that an external electric field can induce phase separation in liquid mixtures, provided that the fields are non-uniform [3]. Variations in the intensity of the electric field are generic and occur in all electrodes unless special care is taken to eliminate them. When a liquid mixture is subjected to such a spatially non-uniform field, the situation is very different from the Landau scenario. The direct coupling between field variations and composition fluctuations gives rise to a dielectrophoretic force that tends to “suck” the component with the higher dielectric constant into the region with the high electric field.
Suppose an A/B binary mixture initially lies in the homogeneous region of a phase diagram, above the coexistence temperature but below Tc, and that the A component has a higher dielectric constant ∈ than the B component. Then, the concentration of the A-liquid will be higher in the high-field region (B will occupy the rest of the space). At a critical field (or voltage), where the composition crosses into the unstable part of the phase diagram, a phase-transition occurs: a sharp interface between the A-rich and the B-rich domains is created, and the mixture is no longer homogeneous in equilibrium. As the voltage is further increased, the location of the front and the compositions of the A-rich and B-rich domains change. The transition line between a homogeneous and a separated mixture thus changes. This change can be 50 to 100 times larger than the change in uniform fields (Landau mechanism). However, one still has to be closer than about 1 degree from the coexistence temperature of the liquids, and apply rather high voltages (˜300V).
In order to make practical application of the results shown in this work, there is a need for a method that will overcome these two problems, i.e. tight temperature regulation and high voltages.
It is therefore a purpose of the present invention to provide method that improves upon the prior art by allowing electric field induced phase separation over a wide range of temperatures and using relatively low voltages.
Further purposes and advantages of this invention will appear as the description proceeds.